Mk6 Wont hold fuel pressure.

[Transit86]

Hi.

I changed my fuel filter on my 2.0tddi Mk6 this week because the service indicator suggested it was required. I followed the general recomendations of warming the van up, filling the replacement filter with fresh diesel when repalcing etc. The van started as normal after the repalcement and sat on the drive idleing for 10 minutes or so without a hickup or cough. I didnt need the van that day so didnt drive it until the following day which was only to move it off the drive. I had to crank the van for a considerable amount of time before it would start. Once it started it ran ok but i only moved it. Today i went to use it and i had the same issue, i had to crank the starter for a such a long time that the battery nearly went flat before it started. Assuming there was still some form of air trapped I took the van for a 20 minute drive and it ran perfectly. When i got home I turned it off and then restarted it with no issues. I did this several times and felt reasonably confident that the issue was resolved. I went back to the van around 45 minutes later and had the same issue again, although i didnt have to crank it quite as long as if id left it overnight.

I had no issues before i did the filter change. I did a glow plug change a month or so ago with no issues afterwards and very positive starting right up until the filter change. Ive read that bleeding after a filter change can be a pain, but from what i have read it seems that if there is an issue its normally that the van wont start afterwards. Mine started perfectly after the filter change, its just been crap every time since!

Ive double checked that the filter is the same as the one i removed. There doesnt appear to be any fuel leaks. The van runs fine once its started.

It feels to me that the fuel presure is dropping off when the van is turned off. Could this be from air still trapped in the system? Ive looked through several forums but cant find a post on this exact issue. Has anyone encountered anything similar?

Thanks in advance for any help on the issue.

[Frag]

Most likely the new filter isn't sealed fully,this allows air in and then fuel will 'symphon' back to the tank,
System needs to be perfectly airtight and sealed as it relies purely on injection pump to 'lift' the fuel from tank all the way to fuel pump.
(Hence no fuel leaks when running)

If air can get in anywhere,when it's stood or left it will drain back to the tank.

Had problems with non-gen fuel filters..... the rubber seal in centre could be seen to be oval and misshaped.
Filter heads have been known to cause issues,I'd suggest a genuine filter first,if not cured you'll need to get some clear pipe to check for air ingress.

[knobby1]

Most likely the new filter isn't sealed fully,this allows air in and then fuel will 'symphon' back to the tank,
System needs to be perfectly airtight and sealed as it relies purely on injection pump to 'lift' the fuel from tank all the way to fuel pump.
(Hence no fuel leaks when running)

If air can get in anywhere,when it's stood or left it will drain back to the tank.

Had problems with non-gen fuel filters..... the rubber seal in centre could be seen to be oval and misshaped.
Filter heads have been known to cause issues,I'd suggest a genuine filter first,if not cured you'll need to get some clear pipe to check for air ingress.

+1..^^

Lord Knobrot

[Transit86]

Problem solved!

Taking the advice above I removed the filter. I discovered that i had fitted it incorrectly. I hadnt lined the lug on the filter up withy the groove in the housing.It had pushed up into place without alignment but was obviously not in the correct orientation and may well have been allowing air through. I refilled with fresh diesel and fitted the filter correctly which solved the issue.

Thanks for the advice.